I. Field of the Invention
The present invention relates to materials for arc welding, and in particular to a flux composition of flux-cored wires for welding steels with a gas-shielded process.
The invention may be used more efficiently in the flux-cored wires designed for automatic and semiautomatic welding in normal, inclined and horizontal positions of the weld seam in a vertical plane.
2. Prior art
Known in the art are flux compositions for flux-cored wires with a lime-type coating designed for welding and surfacing steels with CO.sub.2 -shielded process in all positions, and comprising a steel sheath filled with a powdered flux forming a core thereof. It is worth noting that the best results have been obtained by using a flux-cored wire having a flux core containing the following ingredients, by weight %:
______________________________________ rutile concentrate 31 fluorite concentrate 16 ferromanganese 9 ferrosilicon 2 iron powder 42 (cf. British Patent No. 858,854) ______________________________________
The flux-cored wire having a flux core formed from the above flux composition provides for the formation of a refined weld metal with a small amount of non-metallic inclusions and a low oxygen content. The weld joint thus produced features a high plasticity and notch impact toughness at low temperatures. However, this flux composition contains a great amount of the fluorite concentrate which is introduced therein to prevent hydrogen from dissolving in the weld metal. The high content of the fluorite concentrate is accounted for by its low intensity of binding hydrogen which is present in high amounts in the arc zone, thereby causing formation of pores in the weld metal. Since the fluorite concentrate contains 90% by weight of calcium fluoride (CaF.sub.2) which is known to destabilize arcing, the welding with the use of the above flux-cored wire is accompanied with an intensive spattering of electrode metal.
It is to be noted that welding apparatus operating with alternating loads not always meet conditions of the weld joint formation. In addition, the resulting weld joints have coarse ripples and a bead shape, which lowers their fatigue strength. To improve the latter the resultant weld has to be machined which is associated with additional labour consumption.
The are also known flux compositions for flux-cored wires of the rutile type designed for welding and surfacing steels under CO.sub.2 in different weld positions. The best results in welding have been obtained with the use of the flux-cored wire having a core formed from the flux composition composed of the following ingredients, weight %:
______________________________________ rutile concentrate 18-38 feldspar 0.6-5 sodium fluosilicate 0.6-5.2 ferromanganese 9.5-12.5 ferrosilicon 0.6-1.5 iron powder balance ______________________________________
(cf. USSR Author's Certificate No. 285,801)
The presence of sodium fluosilicate in the above flux composition provides for more active binding of hydrogen which is present in a great amount in the arc zone, sodium fluosilicate not greatly influencing spattering of electrode material. The flux-cored wires having a core formed from the above flux composition provide for a proper formation of the weld seam: the weld seam is formed slightly concaved with a smooth transition to the basic metal. However, the use of sodium fluosilicate which is highly toxical requires additional safety measures in manufacturing flux-cored wires having a core formed from the above flux composition. In addition, welding slag in the case of using the above flux-cored wires has a low basicity, which is responsible for that the resulting weld metal has a relatively higher content of oxygen (0.08 weight %) in the form of oxide non-metallic inclusions, which lowers resistance of the weld joint to the formation of hot cracks and shifts the threshold of its cold shortness to the range of high temperatures.
The principal object of the invention is the provision of a welding flux composition of flux-cored wires for welding and surfacing steels with a gas-shielded process, which would improve welding properties of the flux-cored wires and safety of the production thereof as well as raise mechanical properties of the weld joint in the wide range of temperatures.
Another object of the invention is to improve the stability of arc.
Still another object of the invention is to minimize the oxygen and hydrogen content in the weld metal.
Yet another object of the invention is to produce a weld joint without pores.
A further object of the invention is to minimize the amount of non-metallic inclusions in the weld metal.
Other objects and advantages of the invention will become evident from the following description of specific embodiments thereof.